function [x sign] = signal3(step)
x = -2:step:2;
%SIGNAL3 y = 3(1- 2*|x|) x[-0.5 0.5]
 sign = zeros(1,length(x));
for k = 1:length(x)
    if (x(k)>=-0.5) && (x(k)<=0.5)
        sign(k) = 3*(1-2*abs(x(k)));        
    else sign(k)=0;
    end;
end;